Total parenteral nutrition (TPN) in the low birth weight and term infant commonly leads to significant hepatic injury initially in the form of cholestasis followed by fibrosis, cirrhosis and end stage liver disease. The purpose of the current proposal is to assess which tauroursodeoxycholic acid given prior to development of cholestasis in infants on TPN will prevent the development of liver disease in this "at risk" population. The current focus of the study is to determine whether bile will be enriched with the exogenous bile acid, which is being supplied to subjects under an IND.